1. Field of the Invention
This invention concerns a method for reducing the cloud point of a hydrodewaxed base stock. More particularly, it relates to a method of lowering the cloud point of a base stock by treating same with sulfur to provide a low sulfur concentration, either alone or in the presence of a magnesium, calcium or barium compound.
2. Discussion of the Prior Art
Many hydrodewaxed base oils have relatively high cloud points. While other properties are excellent and the cloud point appears to have no deleterious effect on the performance of formulated oils, nevertheless, there are specification tests for many oils that require that there be no overnight cloud formation in the base oil at a given temperature, often 30.degree. F. to 40.degree. F.
The high cloud point (or overnight cloud point, ONC) is common to many hydrodewaxed oils. Much processing work, such as selective removal of the haze components and use of crystallization inhibitors, has been done with limited success. Generally, solutions to the haze formation are uneconomic or impractical because the solutions introduce other problems such as lower viscosity index, poor storage stability, dark color, water emulsification tendency, poorer oxidation response, and the like.
No prior art is known that teaches or suggests that the herein disclosed useful results can be obtained by reacting a mineral oil base stock with sulfur to give the low sulfur concentrations of the invention. It is known, however, that sulfur has been reacted with mineral oils to produce H.sub.2 S or to provide corrosive oils for cutting purposes or to impart antiwear properties to oils.